The Bureau of Meteorology is predicting the flood situation in south-western New South Wales to worsen, with warnings stepped up on Thursday.

Around 75 per cent of the state is flooded or under threat, while the record rain has created similar emergencies across the ACT and northern Victoria.

Police in Goulburn have knocked on doors and asking people to leave their homes as heavy rain is leading to rises in the Wollondilly and Mulwaree rivers.

While about 200 homes in the city are subject to evacuation orders, hundreds more are subject to evacuation orders at Cooma in the state's south.

The SES has helped to sandbag low-lying areas in both towns and say it is now a matter of waiting to see how much more rain falls.

The Warragamba Dam west of Sydney is expected to reach capacity and spill water for the first time in more than 10 years.

In the saturated Riverina, many smaller creeks have burst their banks and several towns have been inundated in parts.

Numerous roads remain closed and a moderate flood warning is in place for both the Tumut and Murrumbidgee rivers.

Several people were rescued in the biggest flooding to hit the southern town of Tumut in forty years after the Goobarragandra River peaked suddenly.

Some centres have received about 100 millimetres of rain this week, and for some in the region there is still plenty more to come.

Low-lying streets of Queanbeyan are on an evacuation alert as the Molonglo and Queanbeyan rivers continue to rise, but residents did not seem too fazed, having experienced far worse flooding just 14 months ago.

Gundagai is expected to reach minor flood level and will reach a moderate flood level on Friday morning, and Wagga Wagga is now expected to reach the minor flood level on Saturday night.